Inkjet inkset and methods

ABSTRACT

There is disclosed an ink set and method for printing an inkjet ink image on a nonporous substrate. The inkset and method comprise one or more inkjet inks comprising at least one first pigment-based inkjet ink having a first colorant load of a pigment and a polymeric latex binder; and at least one second pigment-based inkjet ink having a second colorant load of the pigment and a polymeric latex binder, the second colorant load being less than the first colorant load, and the second pigment-based inkjet ink applied to a substrate in an amount to provide a total ink loading of from about 10 g/m 2  to about 30 g/m 2 .

CROSS-REFERENCE TO RELATED APPLICATION

The present application is the U.S. National Stage under 35 U.S.C. §371of PCT/US2007/087596, filed 14 Dec. 2007, the disclosure of which ishereby incorporated herein by reference.

BACKGROUND ART

Ink jet printing is a non-impact method for producing images by thedeposition of ink droplets on a substrate (paper, transparent film,fabric, etc.) in response to digital signals. Ink jet printers havefound broad applications across markets ranging from industrial labelingto short run printing to desktop document and pictorial imaging andlarge format printing for outdoor applications such as banners,signages, displays, posters, billboard and bus wraps.

Various types of inks and printing surfaces are available for inkjetprinting. Inkjet ink compositions, which are substantiallyaqueous-based, when used in combination with non-porous/non-absorbentsubstrate surfaces such as vinyl, generally suffer from durabilityissues, including lightfastness, waterfastness, abrasion resistance andweather resistance. In order to overcome these problems, solvent basedinks or UV curable inks were developed to be printed on non-absorbingsubstrates to achieve the desired durability. However, significantenvironmental, health and safety concerns exist with both of these typesof ink, including evaporation of solvent or UV monomer during printing.

Further efforts to overcome durability issues included pre-treatment ofthe media to accept the ink and/or post-treatment to render the imagesufficiently waterfast, lightfast, and/or durable for the intended use,thereby increasing the cost.

Thus it would be desirable to provide an aqueous-based inkjet ink setand printing method for a non-absorbent substrate surface havingenhanced durability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graphical representation of wet rub resistance as a functionof ink loading in accordance with an embodiment of the invention.

FIG. 2 is a graphical representation of wet rub resistance as a functionof color density in accordance with an embodiment of the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of one or more aspects of the disclosure herein. It may beevident, however, that one or more aspects of the disclosure herein maybe practiced with a lesser degree of these specific details.

The disclosure relates to an inkjet ink set and method of printing adurable inkjet image on nonporous substrates. The inkjet image producedby the inkset and method of the invention can have improved durability,including rub resistance.

The phrase “effective amount,” as used herein, refers to the minimalamount of a substance and/or agent, which is sufficient to achieve adesired and/or required effect. For example, an effective amount of a“colorant load” is the minimum amount required in order to create an inkcomposition having the desired properties associated therewith.

The invention is suited for printing on a variety of substrates,especially on non-absorbing substrates or non-porous media. The terms“low-porous media” or “non-porous media” each refer to print media whichhas a Bristow Test of less than 2 ml/m2 at a contact time of less than0.5 s. The Bristow Test (ASTM D5455-93) is known in the art and issummarized below. A test specimen of defined dimensions is affixed tothe smooth rim of a wheel free to rotate at a defined constant speed incontact with a stationary test fluid applicator pressing against thetest specimen with a defined pressure. The test fluid applicatorconsists of a test solution storage compartment affixed above a 1 by15-mm test fluid delivery slot, the slot being positioned so that thelong dimension is perpendicular to the direction of rotation of the rimof the wheel, and parallel to the wheel axis. A defined quantity of testfluid is placed through the fluid reservoir, onto the fluid deliveryslot. With the wheel with the test specimen affixed rotating at constantspeed, the test solution applicator is brought into contact with therotating test specimen and held in place under defined pressure. Thetest fluid is transferred from the test solution applicator onto thetest specimen in a band whose width, controlled by the applicator slotwidth is approximately 15 mm, and whose length is a function of theabsorptive characteristics of the test fluid interaction with the testspecimen under the defined test conditions. The amount of liquidabsorbed per unit area of test specimen is calculated from the volume oftest fluid originally placed in the applicator, and the average widthand length of the band created on the test specimen by the transferredtest fluid. The time available for the liquid absorption is calculatedfrom the volume of test fluid originally placed in the applicator andapplicator geometry.

The non-absorbing substrates that may be used in the invention includeany substrate that is essentially non-porous. They are usually notspecially treated for additional liquid absorption. Therefore, thesematerials have very low or no liquid absorbing capacity. Examples ofsuch non-absorbing substrates are metals such as aluminum, copper,stainless steel and alloy; plastics such as vinyl, polycarbonate,polytetrafluoroethylene (PTFE), polyester, acrylic, polyethylene,polypropylene, polystyrene, cellulose; and other substrates such asceramics, glass and transparency materials.

In accordance with embodiments of the invention, the inkset and methodfor printing inkjet ink images for use with the invention typicallyinclude a liquid vehicle and a colorant, such as a pigment. Optionally,the liquid vehicle can carry other compositions other than the colorant,such as dispersed polymers or the like. “Liquid vehicle” or “inkvehicle,” as used herein, refers to the vehicle in which colorant isplaced to form an ink. A wide variety of ink vehicles may be used withthe inks and methods according to embodiments disclosed herein. It is tobe understood that the ink composition disclosed herein may be anaqueous based ink, an organic based ink, or combinations thereof.Examples of suitable ink vehicles include, but are not limited to watersoluble polymers, surfactants (e.g., non-ionic surfactants, ethoxylatednonionic fluorosurfactants, etc.), solvents, cosolvents, buffers,biocides, sequestering agents, viscosity modifiers, surface-activeagents, chelating agents, resins, and/or water, and/or combinationsthereof.

Various types of pigments can be used, such as self-dispersed pigmentsand/or polymer dispersed pigments. Self dispersed pigments typicallyinclude small molecule or polymeric dispersing agents attached to thesurface of the pigment particulates. If a non self-dispersed pigment isused, then the liquid vehicle can further comprise a dispersing agentthat associates with the pigment, or the pigment can be physicallycoated with the dispersing agent. Dispersing agents can be polymers,oligomers, surfactants, small molecules, or the like.

Pigments can include, but are not limited to, black pigment-based inks,neutral gray pigment-based inks and colored pigment-based inks. By“neutral grey ink” it is meant a black pigment ink that may containother pigments, for example, pigment red, cyan and/or violet, to makethe ink neutral. Colored pigment-based inks can include, but are notlimited to, cyan and magenta.

The following black pigments can be used in the practice of theinvention. This listing is merely illustrative and not intended to limitthe disclosure. The following black pigments are available from Cabot:Monarch™ 1400, Monarch™ 1300, Monarch™ 1100, Monarch™ 1000, Monarch™900, Monarch™ 880, Monarch™ 800, and Monarch™ 700, Cab-O-Jet™ 200,Cab-O-JeFM 300, Black Pearls™ 2000, Black Pearls™ 1400, 15 Black Pearls™1300, Black Pearls™ 1100, Black Pearls™ 1000, Black Pearls™ 900, BlackPearls™ 880, Black Pearls™ 800, Black Pearls™ 700; the following areavailable from Columbian: Raven 7000, Raven 5750, Raven 5250, Raven5000, and Raven 3500; the following are available from Evonik: ColorBlack FW 200, Color Black FW 2, Color Black FW 2V, Color 20 Black FW 1,Color Black FW 18, Color Black S 160, Color Black FW S 170, SpecialBlack 6, Special Black 5, Special Black 4A, Special Black 4, Printex U,Printex 140U, Printex V, and Printex 140V.

The pigment can also be chosen from a wide range of conventional coloredpigments. For the purposes of clarification only, and not forlimitation, some exemplary colorants suitable for this purpose are setforth below.

Non-limiting examples of the magenta pigments include pigment red 5,pigment red 7, pigment red 12, pigment red 48:1, pigment red 48:2,pigment red 48:3, pigment red 48:4, pigment red 48:5, pigment red 48:6,pigment red 57, pigment red 112, pigment red 122, pigment violet 19, andthe like. Non-limiting examples of the cyan pigments includes pigmentblue 1, pigment blue 2, pigment blue 3, pigment blue 15:3, pigment blue16, pigment blue 22, vat blue 4, vat blue 6, and the like. Examples ofsuitable pigments for the neutral gray inks include a black pigment andat least one color pigment (e.g., cyan, violet, magenta, red, orange,yellow, green, or blue pigments, or combinations thereof) dispersedtherein.

The pigments useful in the invention can have any particle sizes whichcan be jetted through a print head. In one embodiment, the pigmentparticles have a particle size of about 30 nm to about 500 nm, and inone embodiment, from about 30 nm to about 150 nm.

In accordance with an embodiment of the invention, the inkset of theinvention will comprise an ink cartridge configured to contain aplurality of pigment-based inkjet inks. At least one first pigment-basedink will have a first colorant load. The term “colorant load”, as usedherein, refers to the amount of pigment present in the ink. In oneembodiment, the first pigment-based ink will comprise a colorant loadeffective to provide a dark ink, for example, magenta, cyan, or blackink. Where the first pigment-based ink comprises magenta, in oneembodiment, the first colorant load will range from about 2.0 wt % toabout 4.5 wt %. In one embodiment, the first colorant load will rangefrom about 2.5 wt % to about 3.5 wt %. In another embodiment, where thefirst pigment-based ink comprises cyan, the first colorant load willrange from about 1.0 wt % to about 2.5 wt % and in one embodiment, thefirst colorant load will range from about 1.25 wt % to about 2.0 wt %.In a further embodiment, where the first pigment-based ink comprisesblack, the first colorant load will range from about 1.0 wt % to about2.75 wt % and in one embodiment, the first colorant load will range fromabout 1.3 wt % to about 2.0 wt %.

In an embodiment, at least one second pigment-based ink will have asecond colorant load. In one embodiment, the second pigment-based inkwill comprise a colorant load effective to provide a light ink of thesame pigment as the corresponding dark ink, for example, light magenta,light cyan, or a neutral grey ink. The second pigment-based ink willcomprise a second colorant load in a range as measured with a dilutionfactor of from about 1:3 to about 1:8 of the corresponding firstpigment-based ink. In one embodiment, the second pigment-based ink willcomprise a second colorant load in a range as measured with a dilutionfactor of from about 1:3 to about 1:6, and in a further embodiment fromabout 1:3 to about 1:4. For example, in one embodiment, the amount ofmagenta pigment has a colorant load sufficient to provide an absorbancemaxima, with values being measured at a 1:10,000 dilution at a cell pathlength of 1 cm, ranging from about 0.01 to about 0.03 at a 1:3-1:8dilution of the first colorant load of magenta ink, at a wavelengthmaxima ranging from about 520 nm to about 550 nm (colorant load rangingfrom about 0.25 wt % to about 1.5 wt %). In another embodiment, theamount of cyan pigment has a colorant load sufficient to provide anabsorbance maxima, with values being measured at a 1:10,000 dilution ata cell path length of 1 cm, in a range from about 0.01 to about 0.03 ata 1:3-1:8 dilution of the first colorant load of cyan ink at awavelength maxima ranging from about 600 nm to about 625 nm (colorantload ranging from about 0.16 wt % to about 0.83 wt %). In anotherembodiment, the amount of tinted grey pigment has a colorant loadsufficient to provide an absorbance maxima, with values being measuredat a 1:10,000 dilution at a cell path length of 1 cm, in the range fromabout 0.01 to about 0.03 at about 500 nm at a 1:3-1:8 dilution of thefirst colorant load of black ink (colorant load ranging from about 0.16wt % to about 0.92 wt %).

In one embodiment, the pigment ink of the invention will contain apolymeric latex binder. Binders can be included which act to secure thecolorants on the substrate. The term “latex” refers to dispersionscomprising a liquid and polymer. Polymeric binders may be either solublein the ink vehicle or dispersed as particulates. The polymericparticulates can have a particle size range from about 100 nm to about300 nm, and in one embodiment from about 200 nm to about 300 nm. Binderssuitable for use in the invention include, but are not limited to aconjugated diene copolymer latex (e.g., styrene-butadiene copolymer,methyl-methacrylate butadiene copolymer), an acrylic polymer latex,vinyl-based polymer latex, polyurethanes, and polyurethane dispersions,among others. In one embodiment, the binder comprises an acrylic polymerlatex.

The amount of binder to be incorporated in the ink will range, in oneembodiment, from about 2 wt % to about 15 wt %. In one embodiment theamount of binder will range from about 4 wt % to about 10 wt %, and inanother embodiment, the binder will range from about 5 wt % to about 7wt %. In one embodiment, the first pigment-based inkjet ink will have afirst colorant load and a first binder load, and the secondpigment-based inkjet ink will have a second colorant load and a secondbinder load. In one embodiment, the second binder load is less than thefirst binder load. In such an embodiment the amount of binder of thefirst binder load will range from about 5 wt % to about 8 wt % and theamount of binder in the second binder load will range from about 2 wt %to about 4 wt %.

In an embodiment of a method of printing an inkjet ink image, anon-porous substrate is established onto which there is jetted a firstpigment based-inkjet ink having a first colorant load of a pigment,followed by jetting of a second pigment-based ink having a secondcolorant load of the same pigment. The amount of the ink establisheddepends, at least in part, on the image to be formed. In one embodiment,the first and second pigment inks are applied at an ink loading of fromabout 10 g/m2 to about 30 g/m2, and in one embodiment from about 14 g/m2to about 25 g/m2. Further, it will be understood, that jetting of thefirst and second pigment inks may occur substantially simultaneously orsequentially.

The image may include alphanumeric indicia, graphical indicia, orcombinations thereof Non-limiting examples of suitable inkjet printingtechniques include continuous, drop on demand, piezoelectric inkjet,thermal inkjet, or combinations thereof

It is to be understood that the image(s) formed from embodiments of theink sets and methods described herein generally exhibit durable imageswith improved rub resistance.

To further illustrate embodiment(s) of the present disclosure, variousexamples are given herein. It is to be understood that these examplesare provided for illustrative purposes and are not to be construed aslimiting the scope of the disclosed embodiment(s).

EXAMPLES

The general composition of pigment-based inkjet inks made according tothe invention is shown in TABLE I, along with ranges of amount ofingredients making up each component. The inkjet ink may be cyan,magenta, or black, depending on the colorant that is used (including thelighter versions of those stated above, i.e., light cyan, light magenta,and gray).

TABLE 1 Ingredients (%) Black Cyan Magenta Lt Cyan Lt Magenta Equivalent1.60% 1.80% 1.97% 0.75% 1.03% Pigment Load (in wt %) Black 0.066 Cyan0.089 0.037 Magenta 0.050 0.026 Acrylic latex 6.00% 6.00% 6.00% 6.00%6.00% 2P 16.00% 16.00% 16.00% 16.00% 16.00% MPDiol 9.00% 9.00% 9.00%9.00% 9.00% perfluoralkyl- 2.00% 2.00% 2.00% 2.00% 2.00%alcoholethoxylate Water Balance Balance Balance Balance Balance

Example 1

Durability Test

Test Sample Preparation

A non-absorbing vinyl substrate, a multi-purpose inkjet cast vinyl wascut into 0.75 by 4 cm in size and placed on a heated coating block withtemperature at about 40° C. The above inks were applied to the heatedvinyl substrates described above. Uniform coatings of the inks wereobtained. The selected samples were then heated at 90° C. for 1 minuteusing an infrared lamp.

Dry Rub Resistance Test

A dry rub resistance test can be carried out by rubbing the samplesusing a CS-10 Weareaser rubber abrasive for 10 passes with a strokelength of 2.0 inches, rub speed of 25 cycles/min, and finger loading of600 g in the inked area. The color loss in the treated sample area andthe color transfer to the cloth can be examined visually and a rating ofthe dry rub resistance is given as follows on a scale of 0 to 5. 0:0=nodamage, 1=gloss loss, 2=0% to 20% colorant loss, 3=20% to 50% colorantloss, 4=50% to 80% colorant loss, and 5=>80% colorant loss.

Wet Rub Resistance Test

A wet rub resistance test was carried out by using a acrylic crockmetercovered with a cloth wetted in a fluid, typically Windex blue glasscleaner. The above treated area was then rubbed with a paper towelwetted with Windex for 6 passes with a stroke length of 2.0 inches, rubspeed of 25 cycles/min, and finger loading of 600 g in the inked area.The color loss in the treated sample area and the color transfer to thepaper towel were examined visually and a rating of the wet rubresistance was given similar as above on a scale of 0 to 5, 0 being thebest and 5 being the worst. The wet rub resistance test results areshown in FIG. 1 as a function of ink loading. As can be seen, theDurability Grade indicated an improvement in wet rub resistance at inkloadings where a second (light) pigment ink was applied in an amount toprovide a total ink loading above 10 g/m². An improvement in DurabilityGrade indicated an improvement in wet rub resistance in ink loadingsusing an increased amount of a second (light) pigment ink, as comparedto normal usage, is seen in FIG. 2.

Although the disclosure has been shown and described with respect to oneor more embodiments and/or implementations, equivalent alterationsand/or modifications will occur to others skilled in the art based upona reading and understanding of this specification. The disclosure isintended to include all such modifications and alterations and islimited only by the scope of the following claims. In addition, while aparticular feature may have been disclosed with respect to only one ofseveral embodiments and/or implementations, such feature may be combinedwith one or more other features of the other embodiments and/orimplementations as may be desired and/or advantageous for any given orparticular application. Furthermore, to the extent that the terms“includes”, “having”, “has”, “with”, or variants thereof are used ineither the detailed description or the claims, such terms are intendedto be inclusive in a manner similar to the term “comprising.”

1. An inkjet ink set, comprising: a first pigment-based inkjet inkhaving a first colorant load of a pigment and a polymeric latex binder;and a second pigment-based inkjet ink having a second colorant load ofthe pigment and a polymeric latex binder, the second colorant load beingless than the first colorant load, the second pigment-based inkjet inkconfigured to be applied to a substrate in an amount to provide a totalink loading of from about 10 g/m² to about 30 g/m², the firstpigment-based inkjet ink comprising a first colorant load and a firstbinder load within a range of from about 5 wt % to about 8 wt % and thesecond pigment-based inkjet ink comprising a second colorant load and asecond binder load within a range of from about 2 wt % to about 4 wt %.2. The inkjet ink set of claim 1, wherein the first and secondpigment-based inkjet inks are configured to be applied to anon-absorbing substrate.
 3. The inkjet ink set of claim 2, wherein thesecond pigment-based inkjet ink is configured to be applied over thefirst pigment based inkjet ink applied on the non -absorbing substrate.4. The inkjet ink set of claim 1, the non-absorbing substrate comprisingone or more of vinyl, polycarbonate, polytetrafluoroethylene (PTFE),polyester, acrylic, polyethylene, polypropylene, polystyrene, cellulose,a metal, a ceramic, or a glass.
 5. The inkjet ink set of claim 1, thebinder comprising a latex of one or more of conjugated diene copolymerlatex, acrylic polymer latex, vinyl-based polymer latex, functionalgroup-modified polymer latex, a polyurethane, or a polyurethanedispersion.
 6. The inkjet ink set of claim 5, the latex bindercomprising a binder load of from about 2 wt % to about 15 wt % and abinder particle size ranging from about 100 nm to about 300 nm.
 7. Theinkjet ink set of claim 1, the first pigment inkjet ink comprising acolorant load effective to provide a dark ink and the second pigmentinkjet ink comprising a colorant load effective to provide a light inkof the same pigment as the corresponding dark ink.
 8. The inkjet ink setof claim 7, the first pigment inkjet ink comprising magenta, cyan, orblack and the second pigment inkjet ink comprising light magenta, lightcyan, or neutral grey.
 9. The inkjet ink set of claim 8, the firstpigment inkjet ink comprising magenta having a first colorant load in arange of from about 2.0 wt % to about 4.5 wt % and the second pigmentinkjet ink comprising light magenta having a second colorant loadsufficient to provide an absorbance maxima with values being measured ata 1:10,000 dilution, ranging from about 0.01 to about 0.03 at a 1:3-1:8dilution of the first colorant load of magenta ink, at a wavelengthmaxima ranging from about 520 nm to about 550 nm.
 10. The inkjet ink setof claim 8, the first pigment inkjet ink comprising cyan having a firstcolorant load in the range of from about 1.0 wt % to about 2.5 wt % andthe second pigment inkjet ink comprising light cyan having a secondcolorant load sufficient to provide an absorbance maxima with valuesbeing measured at a 1:10,000 dilution, ranging from about 0.01 about0.03 at a 1:3-1:8 dilution of the first colorant load of magenta ink, ata wavelength maxima ranging from about 600 nm to about 625 nm.
 11. Theinkjet ink set of claim 8, the first pigment inkjet ink comprising blackhaving a first colorant load of from about 1.0 wt % to about 2.75 wt %and the second pigment inkjet ink comprising tinted grey having a secondcolorant load sufficient to provide an absorbance maxima with valuesbeing measured at a 1:10,000 dilution, ranging from about 0.01 about0.03 at a 1:3-1:8 dilution of the first colorant load of magenta ink, ata wavelength maxima of about 500 nm.
 12. The inkjet ink set of claim 7,the first and second pigment inkjet inks having a pigment particle sizeof from about 30 nm to about 500 nm.
 13. A method of printing an inkjetimage comprising: establishing a non-absorbing substrate; jetting afirst pigment-based inkjet ink having a first colorant load of a pigmentand a polymeric latex binder onto the non-absorbing substrate to form aprinted image thereon, and jetting a second pigment-based inkjet inkhaving a second colorant load of the pigment and a polymeric latexbinder onto the non-absorbent substrate to form a printed image thereon,the second pigment-based ink applied in an amount to provide a total inkloading of from about 10 g/m² to about 30 g/m², the first pigment-basedinkjet ink comprising a first colorant load and a first binder loadwithin a range of from about 5 wt % to about 8 wt % and the secondpigment-based inkjet ink comprising a second colorant load and a secondbinder load within a range of from about 2 wt % to about 4 wt %.
 14. Themethod of claim 13, jetting of the first pigment-based inkjet ink andthe second pigment-based inkjet ink occurring sequentially orsimultaneously.
 15. The method of claim 13, forming a printed imagecomprising printing the inkjet ink composition using continuous, drop ondemand thermal inkjet, piezoelectric inkjet, or combinations thereof.16. The method of claim 13, the first pigment inkjet ink comprisingmagenta, cyan, or black and the second pigment inkjet ink comprisinglight magenta, light cyan, or neutral grey.
 17. A durable inkjet inkprinted image printed by the method of claim 13.